Apple II Super Serial Card

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Apple II Super Serial Card
Manufacturer Apple Computer, Inc.
Year 1981
Type Serial Interface
Original Price
Compatibility II, II+, IIe, IIGS

The Apple II Super Serial Card, commonly abbreviated SSC, provides the Apple ][, ][+, and //e computers with an RS-232-C serial interface for printers, modems, terminals, and other devices. It will also work in a IIGS, although the IIGS has two built-in seral ports. The SSC replaced the earlier Communications Card and Serial Interface Cards from Apple.

The Super Serial Card will work in slots 1 through 7, but is usually placed in slot 1 for use with a printer, slot 2 for use with a modem, or slot 3 for used with a teminal. These are the slot assignments expected by Apple Pascal and most other Apple II software.

A jumper block near the rear of the card is used to select whether a modem or terminal device is attached to the SSC. The triangle printed on the block should point up toward MODEM if a modem is attached, and down toward TERMINAL if a printer or remote terminal is attached. When the jumper block is set to TERMINAL, it alters the signals at the DB25 connector to provide the function of a "null modem adapter" or "modem eliminator."

Two sets of DIP switches are used to control baud rate, data format, parity, linefeeds, etc. Detailed instructions for setting these switches are in the manual. A Reference Card was included with the switch settings and commands for using the card in Communications Mode and Printer Mode.

The SSC was designed for speeds from 50 to 19,200 bits per second, though it's been reported that 115,200 bits per second can be achieved by some cards by writing a $10 into memory location $C0AB.

The 6551 ACIA (Asynchronous Communications Interface Adapter) chip on the SSC doesn't handle hardware handshaking very well at higher speeds, so many of these 6551's were replaced with 65C51A chips, which didn't have that problem.

In addition, a company called Lighting Systems produced a small daughtercard called the Turbo ASB that replaced the SSC's 6551 chip. Turbo ASB allowed throughput of up to 230,400 bits per second. Only a few programs, such as ProTerm, ANSITerm, and Spectrum supported these higher speeds. Lightning Systems still sells the Turbo ASB, but doesn't seem to advertise the fact. Contact GSE-Reactive's support department for information on purchasing a Turbo ASB from the original producers.


Scan of an early Super Serial Card box.

Apple II Super Serial Card Installation and Operating Manual from 1981. [1]

Command Reference Card from the 1981 Super Serial Card manual. [1]

Super Serial Card Users Manual from 1985. [2]

Super Serial Card Errata from Apple, December 1996.

Apple II Miscellaneous Tech Note #3 documents two bugs in the Super Serial Card firmware.

Apple IIe Tech Note #7 gives the pinouts of the 10-pin header on the SSC and the DB25 connector.


  1. 1.0 1.1 file courtesy of
  2. PDF file by Grijan, from Jorge Chamorro Bieling's "Apple II Things" site (now defunct)
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